Adaptive fingerprint scanning

ABSTRACT

Embodiments of the present invention provide an adaptive and intelligent fingerprint scanning device and approach. Specifically, embodiments of the present invention utilize DC resistive image scanning to reduce overall scanning time and energy consumption (e.g., by identifying a targeted scanning area). In a typical embodiment, a scanning device will be provided that includes a scanning area comprised of a set (e.g., at least one) of imaging pixel electrodes (e.g., arranged adjacent to one another in a grid- like or other fashion). As a user presses his/her finger against the scanning area, a first portion of the finger will contact a first electrode while a second portion of the finger will contact a second electrode. When this occurs, a voltage source of the device will apply an initial voltage across the first and second finger portions. A meter of the device will take an electrical measurement (e.g., resistance and/or charged skin voltage) across the two finger portions. Based on the electrical measurement, a location of the finger on the device will be identified, and the fingerprint will be scanned accordingly. Thus, the entire scanning surface need not be scanned, only the portions thereof where the finger was detected.

FIELD OF THE INVENTION

In general, the present invention relates to fingerprint scanning.Specifically, the present invention relates to a device and method forreducing fingerprint scanning time and associated energy consumption.

BACKGROUND OF THE INVENTION

As global security concerns continue to grow, fingerprint scanning foridentity verification is becoming an often used tool for identityverification. Existing fingerprint imaging methods are based on fullimage scanning, which is not only time consuming (especially whenperformed across a large sample size), but also energy inefficient.Heretofore, several unsuccessful attempts have been made to addressthese shortcomings.

U.S. Pat. Nos. 7,519,204, 7,231,078, 6,741,729, 6,125,192, and 6,097,035disclose a method and apparatus for fingerprint recognition.

U.S. Pat. No. 6,512,381 discloses a fingerprint sensing circuit.

U.S. Pat. No. 5,864,296 discloses a fingerprint ridge, sensor- baseddetector.

U.S. Pat. No. 7,864,992 discloses a fingerprint sensor element thatmeasures sensor point capacitance.

U.S. Pat. Nos. 6,643,389, 6,580,816, and 6,317,508 disclose a capacitivesemiconductor array for fingerprint detection.

U.S. Pat. No. 6,633,656 discloses a fingerprint sensor comprised of anarray of microthermistor devices which convert temperature conditionsinto electrical signals.

U.S. Pat. No. 6,414,297 discloses a fingerprint reading apparatus.

U.S. Pat. No. 4,429,413 discloses a fingerprint sensor for creating anelectrical output signal based upon the topological pattern of a finger.

U.S. Patent Application 20050226478 discloses a fingerprint sensor thatuses a capacitance detecting circuit.

U.S. Patent Application 20050163350 discloses a fingerprint sensingapparatus.

None of these references, however, teach a way to detect a targetedscanning area of a fingerprint so as to avoid wasted scanning time andunnecessary energy consumption by scanning an entire scanning area of adevice.

SUMMARY OF THE INVENTION

In general, the embodiments of the present invention provide an adaptiveand intelligent fingerprint scanning device and approach. Specifically,embodiments of the present invention utilize DC resistive image scanningto reduce overall scanning time and energy consumption (e.g., byidentifying a targeted scanning area). In a typical embodiment, ascanning device will be provided that includes a scanning area comprisedof a set (e.g., at least one) of imaging pixel electrodes (e.g.,arranged adjacent to one another in a grid-like or other fashion). As auser presses his/her finger against the scanning area, a first portionof the finger will contact a first electrode while a second portion ofthe finger will contact a second electrode. When this occurs, a voltagesource of the device will apply an initial voltage across the first andsecond finger portions. A meter of the device will take an electricalmeasurement (e.g., resistance and/or charged skin voltage) across thetwo finger portions. Based on the electrical measurement, a location ofthe finger on the device will be identified, and the fingerprint will bescanned accordingly. Thus, the entire scanning surface need not bescanned, only the portions thereof where the finger was detected.

A first aspect of the present invention provides a method of scanningfingerprints, comprising: applying an initial voltage to a first imagingpixel electrode, the first imaging pixel electrode being in contact witha first portion of a finger; and determining an electrical measurementacross the first imaging pixel electrode and a second imaging pixelelectrode in response to the applying of the initial voltage, the secondimaging pixel electrode being in contact with the second portion of afinger.

A second aspect of the present invention provides a method of scanningfingerprints, comprising: applying an initial voltage to a first imagingpixel electrode, the first imaging pixel electrode being in contact witha first portion of a finger; and determining an electrical measurementacross the first imaging pixel electrode and a second imaging pixelelectrode in response to the applying of the initial voltage, the secondimaging pixel electrode being in contact with the second portion of afinger, and the second imaging pixel electrode being non-adjacent to thefirst imaging pixel electrode; determining a location of a finger on ascanning device based on the electrical measurement; and scanning afingerprint from the finger at the location.

A third aspect of the present invention provides a device for scanningfingerprints, comprising: a set of imaging pixel electrodes for creatinga fingerprint scanning surface; a voltage source coupled to the set ofimaging pixel electrodes for supplying an initial voltage; and a metercoupled to the set of imaging pixel electrodes for taking an electricalmeasurement across a first imaging pixel electrode and a second imagingpixel electrode of the set of imaging pixel electrodes.

A fourth aspect of the present invention provides an adaptivefingerprint scanning method, comprising: grouping a set of imaging pixelelectrodes of a fingerprint scanning device into a plurality of groups;detecting a presence of a finger on at least one of the plurality ofgroups; and performing an adaptive fingering scanning of the at leastone of the plurality of groups.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will be more readilyunderstood from the following detailed description of the variousaspects of the invention taken in conjunction with the accompanyingdrawings in which:

FIG. 1 depicts a fingerprint scanning device according to an embodimentof the present invention.

FIG. 2 depicts fingerprint scanning device according to anotherembodiment of the present invention.

FIG. 3 depicts a scanning area for scanning a fingerprint according toan embodiment of the present invention.

FIG. 4 depicts a finger detection area according to an embodiment of thepresent invention.

FIG. 5 depicts a diagram of adaptive finger locating detection accordingto an embodiment of the present invention.

FIG. 6 depicts a diagram of a two-way electrical sensing array accordingto an embodiment of the present invention.

FIG. 7 depicts a method flow diagram according to an embodiment of thepresent invention.

FIG. 8 depicts a method flow diagram according to an embodiment of thepresent invention.

FIG. 9 depicts a method flow diagram according to an embodiment of thepresent invention.

FIG. 10 depicts a method flow diagram according to an embodiment of thepresent invention.

The drawings are not necessarily to scale. The drawings are merelyschematic representations, not intended to portray specific parametersof the invention. The drawings are intended to depict only typicalembodiments of the invention, and therefore should not be considered aslimiting the scope of the invention. In the drawings, like numberingrepresents like elements.

DETAILED DESCRIPTION OF THE INVENTION

Illustrative embodiments will now be described more fully herein withreference to the accompanying drawings, in which exemplary embodimentsare shown. This disclosure may, however, be embodied in many differentforms and should not be construed as limited to the exemplaryembodiments set forth herein. Rather, these exemplary embodiments areprovided so that this disclosure will be thorough and complete and willfully convey the scope of this disclosure to those skilled in the art.In the description, details of well-known features and techniques may beomitted to avoid unnecessarily obscuring the presented embodiments.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of this disclosure.As used herein, the singular forms “a”, “an”, and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. Furthermore, the use of the terms “a”, “an”, etc., do notdenote a limitation of quantity, but rather denote the presence of atleast one of the referenced items. It will be further understood thatthe terms “comprises” and/or “comprising”, or rectify “includes” and/or“including”, when used in this specification, specify the presence ofstated features, regions, integers, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, regions, integers, steps, operations, elements,components, and/or groups thereof.

A biometric finger scanner is a device that scans a fingerprint andkeeps a record of it. For example, when a door is closed or a computeris shut down, a scanning device can be used to open the door or turn thedevice back on. A person whose fingerprint is stored as a valid accesskey is scanned when they put their finger on the scanning device. If itmatches one of the “approved” fingerprints, access is granted.

The benefits of a biometric finger scanner revolve around the fact thatit is nearly impossible to duplicate another person's fingerprint in aform that the scanner will recognize. Other types of access controlsolutions have a weakness in that they depend on something that caneasily be lost, shared or duplicated. Another strength in fingerprintrecognition is that, in the case of providing access through a door,whoever has an approved fingerprint does not necessarily have access toany other part of the security system. Anyone with the key to any doorhas access to a wealth of information: the manufacturer of the lock andpossibly the model, the type of keys used at the facility, and, in theworst case scenario, possible access to a master-level key that can openmore than one door.

In general, fingerprint scans convert people's fingerprints into digitalcodes or numerical data that can be recorded in a database. Like facialrecognition software, fingerprint scanning matches an individual's codeagainst an existing database of codes in order to confirm thatindividual's identity. Proponents of fingerprint scanning point to theconversion of fingerprints into digital data as a privacy protectionmeasure. Since replicas of fingerprints themselves are never saved, butalways converted, fingerprint data cannot be stolen or mishandled.

One issue surrounding the growing use of fingerprint scanning is thetime required to scan multiple people, and the associated energyconsumption. For example, previous approaches relied upon a scanning ofan entire scanning area (e.g., a pad) even though a person's fingermight only occupy a portion of the scanning area. Scanning an entirescanning area not only wastes time, but could also result in thescanning of unintentional anomalies.

As indicated above, embodiments of the present invention provide anadaptive and intelligent fingerprint scanning device and approach thatprovides targeted fingerprint scanning. Specifically, embodiments of thepresent invention utilize DC resistive image scanning to reduce overallscanning time and energy consumption (e.g., by identifying a targetedscanning area). In a typical embodiment, a scanning device will beprovided that includes a scanning area comprised of a set (e.g., atleast one) of imaging pixel electrodes (e.g., arranged adjacent to oneanother in a grid-like or other fashion). As a user presses his/herfinger against the scanning area, a first portion of the finger willcontact a first electrode while a second portion of the finger willcontact a second electrode. When this occurs, a voltage source of thedevice will apply an initial voltage across the first and second fingerportions. A meter of the device will take an electrical measurement(e.g., resistance and/or charged skin voltage) across the two fingerportions. Based on the electrical measurement, a location of the fingeron the device will be identified, and the fingerprint will be scannedaccordingly. Thus, the entire scanning surface need not be scanned.Rather, only the portions thereof where the finger was first detectedneed be scanned.

Referring now to FIG. 1, a fingerprint scanning device 10 according toone embodiment of the present invention is shown. As depicted, device 10comprises a set of imaging pixel electrodes/ports/sensors 12A-D forcreating a scanning surface, a resister 16 coupled to imaging pixelelectrodes 12B and 12D, a voltage source 20 and a meter 22 coupled toimaging pixel electrode 12B. Device 10 can further include a set ofgrounds 18.

In a typical embodiment, voltage source 20 will apply an initial voltage(e.g., a low-voltage DC bias) to imaging pixel electrode 12B. As shown,imaging pixel electrode 12B is in contact with a first portion 14A of afinger 14. Then, the resistance across finger portions 14A and 14C(e.g., across imaging pixel electrode 12B and imaging pixel electrode12D) will be measured in response to the applying of the initialvoltage. As further shown, imaging pixel electrode 12D is in contactwith a second portion 14C of finger 14. It is not necessary for portions14A and 14C to be contacting adjacent imaging pixel electrodes. Incontrast, portions 14A-C can contact non- adjacent imaging pixelelectrodes 12B and 12D as shown in FIG. 1. Regardless, the measurementof the resistance will allow the presence and location of finger 14 on adevice 10 to be determined/detected (e.g., based on the measuredresistance). Once determined, a fingerprint will be scanned from finger14 at the detected location.

Referring now to FIG. 2, a fingerprint scanning device 30 according toanother embodiment of the present invention is shown. As depicted,device 30 comprises a set of imaging pixel electrodes/ports/sensors32A-D for creating a scanning surface, a voltage source 38 coupled toimaging pixel electrode 32B and a meter 40 coupled to imaging pixelelectrode 32D. Device 30 can further include a ground 36 coupled toimaging pixel electrode 32B and/or voltage source 38.

In a typical embodiment, voltage source 38 will apply an initial voltage(e.g., a low voltage DC bias) to imaging pixel electrode 32B. As shown,imaging pixel electrode 32B is in contact with a first portion 34A of afinger 34. Then, the charged skin voltage across finger portions 34A and34C (e.g., across imaging pixel electrode 32B and imaging pixelelectrode 32D) will be measured in response to the applying of theinitial voltage. Specifically, as further shown, imaging pixel electrode32B is in contact with a second portion 34C of finger 34. It is notnecessary for portions 34A and 34C to be contacting adjacent imagingpixel electrodes. In contrast, portions 34A- C can contact non-adjacentimaging pixel electrodes 32B and 32D. Regardless, the measurement of theresistance will allow the presence and location of finger 34 on a device30 to be determined/detected (e.g., based on the measured resistance).Once determined, a fingerprint will be scanned from finger 34 at thedetected location.

Referring now to FIG. 3, these concepts are illustrated in conjunctionwith scanning area 50. In general, scanning area 50 comprises amatrix/array of imaging pixel electrodes/ports/sensors such as thoseshown in FIG. 1-2. In general, the approaches of FIG. 1 and/or FIG. 2 oftaking an electrical measurement (e.g., resistance or charged skinvoltage) allow for the identification of a targeted scanning area orlocation within scanning area 50 where a finger is actually present. Asdepicted, scanning area 50 comprises imaging pixel electrodes/zone 52where no finger portion was detected, and imaging pixel electrodes/zone56 (numbers 1, 3, 5, 7, 10, 12, and 14) where a finger portion wasdetected. Scanning area can also allow for a buffer zone between thezones such as imaging pixel electrodes/zone 54 (numbers 2, 4, 6, 8, 9,11, 13, and 15), which may represent an area between two finger portionssuch as imaging pixel electrode 12C of FIG. 1 and/or imaging pixelelectrode 32C of FIG. 2 (corresponding to finger portions 14B and 34B,respectively) where scanning may still be prudent. Voltage can beapplied at any imaging pixel electrode such as imaging pixel electrode58. In a typical embodiment, the voltage source remains at “1”, andscanning moves through pixels, along the detected pattern. Theseembodiments reduce readout scanning time when there are limited dataconverter resources. In the example shown in FIG. 3, 15 of 25 imagingpixel electrodes (60%) are scanned, which thus reduces overall scanningtime by 40%. That is, isolated imaging pixel electrodes can be ignoredand not scanned. As such, the process provided by the embodiments of thepresent invention is adaptive and multi-step: (1) detect the presence ofa finger; and scan a fingerprint from the finger using informationobtained by the presence detection in an adaptive process. It isunderstood that in a typical embodiment, the imaging pixel electrodes ofthe present invention can be 300 dpi or more in size.

Referring now to FIG. 4, a diagram depicting large area finger detectionaccording to an embodiment of the present invention is shown. Asdepicted, imaging pixel electrodes 60 (shown in a column-tow matrix) canbe grouped into one or more groups or nodes 62A-B. This will allow amore accurate and economical detection of a finger. After fingerdetection each node 62A-B can perform fingerprint pattern scanning.

Referring now to FIG. 5, a diagram depicting adaptive finger locationdetection according to an embodiment of the present invention is shown.Specifically, FIG. 5 depicts one of the nodes of FIG. 4. In general,adaptive finger location is detected using two groups of commonlyconnected nodes. Along these lines, a group/node is typically comprisedof 5×5 sensors/ports/imaging pixel electrodes 82, although this can bevaried (e.g., 6×6, etc.). In a typical embodiment, a voltage is appliedto group/node 1, and resistance and/or voltage is measured onsurrounding groups/nodes. Using the rough scanning of 5×5 sensor arrays,nine groups/nodes 74 and 76 (e.g., numbers 1-9) of matrix 70 aregenerally found useful and other groups/nodes 78 and 80 (10-25 and theun-numbered groups) can be ignored for fingerprint scanning.Specifically, the following algorithm can be implemented hereunder foradaptive finger location detection:

5×5 sensors (to a single node)=25 sensors

Then the fingerprint scanning that follows can be represented by:

3×3 nodes×5×5 sensors=225 sensors

Thus, the saved scanning time can be represented as follows:

(5×5×6×6)−5×5−(3×3×5×5)=900−25−225=650

650/900=72% scanning saved by finger detection

Referring now to FIG. 6, an electrical sensing array 90 according to anembodiment of the present invention is shown. As shown, array 90comprises nodes 92A-N. In general, each electric sensing node can beaccessed by two independent electrical accesses. As such, two nodes canbe accessed independently for electrical sensing.

Referring now to FIG. 7, a method flow diagram according to anembodiment of the present invention is shown. In step S1, an initialvoltage is applied to a first imaging pixel electrode, the first imagingpixel electrode being in contact with a first portion of a finger. Instep S2, an electrical measurement is determined across the firstimaging pixel electrode and a second imaging pixel electrode in responseto the applying of the initial voltage. As shown above, the secondimaging pixel electrode is in contact with the second portion of afinger. In step S3, it is determined, based on the electricalmeasurement, whether a finger is detected. If not, the process can end.If a finger is detected, a location of finger on the scanning device isdetermined based on the electrical measurement in step S4. Then, in stepS5, a fingerprint is scanned/obtained from the finger at the determinedlocation.

Referring now to FIG. 8, a more detailed diagram of an adaptivefingerprint scanning process is shown. As depicted, in step T1, a sensorand a control integrated circuit (IC) is powered-up. In step T2, afinger is placed on a screen/scanning surface. In step T3, fingerlocation detection occurs. In step T4, a skin-contacted imaging pixelelectrode is found. In step T5, movement around the pixel occurs. Instep T6, it is determined whether contact is made. If so, movement isrepeated in the same direction in step T7. If no contact was made, it isdetermined in step T8 whether there is more to scan in a trace. If so,the process returns to step T5. If not, it is determined in step T9whether all areas have been covered. If not, the process returns to stepT4.

Referring now to FIG. 9, the finger location detection process of stepT3 of FIG. 8 is shown in greater detail. In step U1, a voltage isapplied to a center group as a reference. In step U2, movement (e.g.,voltage movement) around the group is applied. In step U3, it isdetermined whether contact was made. If so, movement in the samedirection is made in step U4. If not, it is determined if additionalsearching is needed in step U5. If so, the process returns to step U2.

Referring now to FIG. 10, the contacted-pixel search for a pattern scanprocess of step T4 of FIG. 8 is shown. As depicted, an unsearched areain the fingerprint scanner is detected in step V1. In step V2, a medianpoint is set. In step V3, a skin-contacted pixel is found. In step V4,it is determined whether contact has been made. If not, thecorresponding area of the scanner can be marked as a “no contact area”in step V5. IF contact was made, the actual finger print scanning can becommenced in step V6.

The foregoing description of various aspects of the invention has beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed and, obviously, many modifications and variations arepossible. Such modifications and variations that may be apparent to aperson skilled in the art are intended to be included within the scopeof the invention as defined by the accompanying claims.

1. A method of scanning fingerprints, comprising: applying an initialvoltage to a first imaging pixel electrode, the first imaging pixelelectrode being in contact with a first portion of a finger; anddetermining an electrical measurement across the first imaging pixelelectrode and a second imaging pixel electrode in response to theapplying of the initial voltage, the second imaging pixel electrodebeing in contact with the second portion of a finger.
 2. The method ofclaim 1, the determining comprising determining a resistance across thefirst portion and the second portion in response to the applying of theinitial voltage to the first imaging pixel electrode.
 3. The method ofclaim 2, the initial voltage being applied via a voltage source coupledto the first imaging pixel electrode, and the resistance beingdetermined via a meter coupled to the first imaging pixel electrode. 4.The method of claim 1, the determining comprising determining a chargedskin voltage across the first portion and the second portion in responseto the applying of the initial voltage to the first imaging pixelelectrode.
 5. The method of claim 4, the initial voltage being appliedvia a voltage source coupled to the first imaging pixel electrode, andthe charged skin voltage being determined via a meter coupled to thesecond imaging pixel electrode.
 6. The method of claim 1, the firstimaging pixel electrode and the second imaging pixel electrode beingamong a plurality of imaging pixel ports of a device for carrying outthe method.
 7. The method of claim 6, the first imaging pixel port andthe second imaging pixel port being non-adjacent to one another amongthe plurality of imaging pixel ports.
 8. The method of claim 1, furthercomprising: determining a location of a finger on a scanning devicebased on the electrical measurement; and scanning a fingerprint from thefinger at the location.
 9. A method of scanning fingerprints,comprising: applying an initial voltage to a first imaging pixelelectrode, the first imaging pixel electrode being in contact with afirst portion of a finger; and determining an electrical measurementacross the first imaging pixel electrode and a second imaging pixelelectrode in response to the applying of the initial voltage, the secondimaging pixel electrode being in contact with the second portion of afinger, and the second imaging pixel electrode being non- adjacent tothe first imaging pixel electrode; determining a location of a finger ona scanning device based on the electrical measurement; and scanning afingerprint from the finger at the location.
 10. The method of claim 9,the determining comprising determining a resistance across the firstportion and the second portion in response to the applying of theinitial voltage to the first imaging pixel electrode.
 11. The method ofclaim 10, the initial voltage being applied via a voltage source coupledto the first imaging pixel electrode, and the resistance beingdetermined via a meter coupled to the first imaging pixel electrode. 12.The method of claim 9, the determining comprising determining a chargedskin voltage across the first portion and the second portion in responseto the applying of the initial voltage to the first imaging pixelelectrode.
 13. The method of claim 12, the initial voltage being appliedvia a voltage source coupled to the first imaging pixel electrode, andthe charged skin voltage being determined via a meter coupled to thesecond imaging pixel electrode.
 14. The method of claim 9, the firstimaging pixel electrode and the second imaging pixel electrode beingamong a plurality of imaging pixel ports of a device for carrying outthe method.
 15. A device for scanning fingerprints, comprising: a set ofimaging pixel electrodes for creating a fingerprint scanning surface; avoltage source coupled to the set of imaging pixel electrodes forsupplying an initial voltage; and a meter coupled to the set of imagingpixel electrodes for taking an electrical measurement across a firstimaging pixel electrode and a second imaging pixel electrode of the setof imaging pixel electrodes.
 16. The device of claim 15, the meter beingconfigured to take the electrical measurement across a first portion ofa finger contacting the first imaging pixel electrode and a secondportion of the finger contacting the second imaging pixel electrode. 17.The device of claim 16, the electrical measurement comprising aresistance across the first portion and the second portion that is takenby the meter in response to the applying of the initial voltage to thefirst imaging pixel electrode.
 18. The device of claim 17, the voltagesource and the meter being coupled to the first imaging pixel electrode.19. The device of claim 15, the electrical measurement comprising acharged skin voltage across the first portion and the second portionthat is taken by the meter in response to the applying of the initialvoltage to the first imaging pixel electrode.
 20. The device of claim19, the voltage source being coupled to the first imaging pixelelectrode, and the meter being coupled to the second imaging pixelelectrode.
 21. An adaptive fingerprint scanning method, comprising:grouping a set of imaging pixel electrodes of a fingerprint scanningdevice into a plurality of groups; detecting a presence of a finger onat least one of the plurality of groups; and performing an adaptivefingering scanning of the at least one of the plurality of groups. 22.The adaptive fingerprint scanning method of claim 21, each of theplurality of groups comprising a 5×5 matrix of imaging pixel electrodes.23. The adaptive fingerprint scanning method of claim 21, the performingcomprising ignoring groups of the plurality of groups where the presenceof the finger was not detected.
 24. The adaptive fingerprint scanningmethod of claim 21, further comprising applying a voltage to a centergroup of the plurality of groups, the detecting being based on theapplying.